The study found that people frayed by even slight distress, meaning they sometimes stayed awake at night worrying or had trouble concentrating on tasks, for example, were about 20% more likely to die over a 10-year period compared to people who reported no such symptoms.

That was true even after researchers adjusted their results to account for unhealthy behaviors that often accompany anxiety and depression, like smoking and excessive drinking. They also accounted for things like exercise, weight, and diabetes.

The study can’t prove that being anxious or depressed leads directly to a person’s death. Other studies looking into the connection have been unable to discover which comes first: Does a person get sick because they’re depressed? Or do people get depressed because they’re sick?

In this study, though, researchers discounted all early deaths — those that happened in the first five years of the study. That makes it less likely that illness caused people to become worried and depressed.

“It is a very impressive study,” says Glyn Lewis, PhD, professor of psychiatric epidemiology at the University of Bristol in the U.K. Lewis wrote an editorial on the study but wasn’t involved in the research.

Anxiety, Depression, and the Risk of Death

For the study, which is published in the journal BMJ, researchers pooled information on more than 68,000 adults over age 35 who took part in England’s National Health Survey from 1994 to 2004.

Each person who participated completed a 12-question mental health survey. The survey asked about things like having trouble concentrating; losing sleep over worry; feeling useful, capable, or under strain; having trouble overcoming difficulties; not enjoying activities; being able to face their problems; feeling unhappy, depressed or worthless; or lacking self-confidence.

Researchers then divided the scores into four groups. People with a score of zero weren’t distressed at all. They were used for comparison. Those who scored one to three on the test were considered mildly distressed. These people had some symptoms of anxiety and depression, but they wouldn’t necessarily have come to a doctor’s attention for their troubles. Scores of four to six were in the range that people might be clinically depressed or anxious. Scores of seven to 12 were people who had been severely distressed.

Researchers then linked the information on the people in the study to British death records. More than 8,300 people in the study died, most from heart disease or stroke (3,382), followed by cancer (2,552) and so-called “external” causes — mostly accidents and injuries (386).

The more depression and anxiety a person reported having, the more likely they were to die.

People with mild distress were about 29% more likely to die of heart disease or stroke than people who reported no distress. Mild distress didn’t seem to raise the risk for cancer.

People with moderate levels of distress were about 43% more likely to die of any cause. And people with high levels of distress were 94% more likely to die during the study than people with no distress.

“We saw a very clear association across the full range of distress,” says researcher Tom C. Russ, MD, a clinical research fellow at the University of Edinburgh in the U.K.

“Even these low levels of symptoms that you might just dismiss as just part of life or whatever still were associated with an increased risk of mortality,” Russ says. “It’s just a message that we need to take these things more seriously.”

Reducing Distress

The study findings did not surprise Viola Vaccarino, MD, PhD, a cardiologist and professor of medicine at Emory University in Atlanta who studies the role of depression in heart disease.

“Clearly there is evidence that depression is a risk factor for cardiovascular disease and total mortality as well,” says Vaccarino, who was not involved in the research. “This study is one of many that have found this type of association.”

Some studies have shown that practices like meditation, which encourage relaxation, can improve risk factors for heart disease, like high blood pressure. But none have yet shown that reducing stress will help a person live longer or make them less likely to die of heart disease.

“There’s no clear solution and no clear link to improved outcomes if you treat these symptoms,” she says. “It’s very complex.”

Until more is known, it’s probably not a bad idea to take steps to protect your health, Vaccarino says.

People who are living with anxiety or depression may find that “talk” therapy, exercise, and other techniques like meditation can help reduce their distress.

SOURCES:Russ, T. BMJ, July 31, 2012.Lewis, G. BMJ, July 31, 2012.Glyn Lewis, PhD, professor of psychiatric epidemiology, University of Bristol, Bristol, U.K.Tom C. Russ, MD, clinical research fellow, University of Edinburgh, Edinburgh, U.K.Viola Vaccarino, MD, PhD, professor and chair, department of epidemiology, Rollins School of Public Health; cardiologist and professor of medicine, Emory University School of Medicine, Atlanta.